Electrical machines, especially rotating electrical machines, comprise an electrical winding within a lamination stack. This consists of electrical conductors (which may already have been provided with a primary insulation) and solid insulation materials as main insulation. Without any further measures, there is no intimate connection between the lamination stack, the conductors, and the main insulation; the lack gives rise to gaps and cavities. In operation under atmospheric conditions, these regions are typically filled with air. Particularly in the case of applications in the high-voltage sector, this cannot be allowed, since partial electrical discharges would destroy the insulation within a very short time. This leads to failure of the electrical machine.
To bring about an intimate bond and the resulting displacement of air, the winding may be impregnated with a hardenable impregnating resin or impregnating lacquer which is thermally hardened, for example, in an air circulation oven. The solid insulation materials may be installed in porous form to increase the impregnation resin uptake. Examples for this purpose are mica tapes, insulation papers, and/or fleeces.
For the impregnation of machines with nameplate voltages greater than 1 kV, typical insulation systems may be composed of solid insulation materials, impregnating resin consisting of base resin and hardener components, which are used in a vacuum pressure impregnation (VPI) process. Often, acid anhydrides are used for this purpose, which serve as hardener and simultaneously lower the viscosity, the benefit of which is rapid and complete impregnation.
However, mixtures of EP resins and the known hardener components do not harden spontaneously even at elevated temperature, but require a hardening-promoting accelerator or catalyst. Tertiary amines, quaternary onium salts, or zinc naphthenate are catalysts employed, as known from DE3824254A1, DE3003477A1, and/or WO 00/24006.
DE 102014219844.5 discloses an insulation system comprising solid insulation materials and an impregnating resin, wherein the impregnating resin is any reactive resin having oxirane functionalities or a mixture of various reactive resins having oxirane functionalities, and at least one thermally activatable and/or encapsulated hardening catalyst is present in the insulation system.